a) Field of the Invention
This invention relates to an underwater anti-fouling agent effective in preventing aquatic organisms such as algae, barnacles and hard-shelled mussels from attaching themselves on objects maintained in contact with seawater, such as ships, ocean rigs and fish nets, and also to an anti-fouling paint making use of the underwater anti-fouling agent.
b) Description of the Related Art
In general, ships' bottoms, ocean rigs, fish nets, fish preserves and the like are maintained in contact with seawater for extended time. During these periods, submarine organisms such as algae, barnacles and hard-shelled mussels attach themselves on seawater-contacting surfaces of such objects, leading to problems such as lowered running speeds due to increases in weight and stream resistance in the case of ships and significantly shortened useful life in the case of fish nets and ocean rigs. Accordingly, a variety of methods have been applied to date for the prevention of attachment of submarine organisms. Known chemical or biochemical methods include, for example, use of materials on which the above submarine organisms are difficult to attach and use of repellents, anti-fouling agents and the like for submarine organisms, such as copper plates, silicone resin paints and fluorine-containing paints. Among such anti-fouling methods, it is the common practice to coat the above-mentioned ships and the like with anti-fouling paints containing anti-fouling agents, because inter alia this coating method is applicable in a wide range of fields, can bring about high effects and can be easily applied. Anti-fouling paints have been available conventionally, each of which is formed of a binder component--which is composed of a seawater-insoluble polymer such as an acrylic resin, alkyd resin or chlorinated rubber and rosin--and an anti-fouling agent such as an organotin compound, organotin polymer or copper suboxide added therein.
A paint with an organotin compound or organotin polymer contained therein is designed in such a way that the organotin compound or organotin polymer in the paint is gradually eluted into water or the paint containing the organotin compound or organotin polymer therein is scraped off little by little to spread in water and always to expose a new paint surface. Despite its high preventive effects against the attachment of underwater organisms, it is accompanied by problems from the standpoint of safety and sanitation and also environmental preservation in that the organotin compound or organotin polymer is eluted into water.